Effect of Age on Bronchial Reactivity in Children with Asthma

Abstract

In contrast to an abundance of data concerning age-related changes of bronchial sensitivity, the relationship between age and rapidity of bronchoconstriction (bronchial reactivity) remains unclear. We studied age and bronchial reactivity in children with asthma. Enrolled in this study were 511 asthmatic subjects and 115 age-matched control subjects 1 to 16 years of age. Bronchial reactivity was represented by the slope of the methacholine transcutaneous oxygen pressure dose-response curve (SPO₂) in younger children and the slope of the respiratory resistance dose-response curve (SRrs) in older children. Overall, SPO₂ and SRrs were higher in asthmatic than control subjects. SPO₂ increased significantly from 1 to 6 years in asthmatic subjects, reaching a plateau after age 7. This age-related change in SPO₂ also was seen in controls. SRrs in asthmatic subjects decreased after age 13, while SRrs in controls showed no significant change between age 7 and 16. Age-related change in bronchial reactivity occurs during childhood, possibly reflecting early changes in airway smooth muscle maturity and later changes in airway wall rigidity.

Keywords:

• bronchial reactivity
• childhood asthma
• methacholine inhalation challenge
• oscillation technique
• transcutaneous oxygen pressure